Maybe it is possible to teach energy, because I can certainly point to some teachers who influenced me–all the way down to that rocking motion I do in lieu of actually bouncing up and down.

That was what he did: rock back and forth, swinging his hands, whenever he got really excited about something: Linux, computer science, mathematics, the joys of algorithms, the search for Rachmaninoff sheet music, the trials and tribulations of his students’ love lives.

In all our classes, he always smiled. I don’t know how he managed to sound happy even while expressing exasperation over test scores or proprietary software companies’ antics, but he did. And one of the best things about being on the “computer science varsity”–the training team for the programming competitions–was training with him and the others during summers.